"Malicious attackers could exploit the flaws to cause a denial-of-service attack, which in turn may allow them to take remote control of a user's system, according to an alert from security research company Secunia, which rates the flaw as "highly critical."

The flaws may be exploited when people attempt to engage a deleted component with designMode turned on. While this typically will crash the browser, it could also result in an attacker running malicious code, according to a Mozilla security advisory. Mozilla oversees the development of the Firefox browser."